This is clownassembler, an assembler for Motorola 68000 assembly language. It mimics the behaviour of SN 68k (also known as 'asm68k').
Being a reimplementation of SN 68k, documentation for that assembler applies to this assembler as well:
http://antime.kapsi.fi/sega/files/SATMAN.pdf
This assembler is written in portable ANSI C (a.k.a. C89), and so should be able to be built with virtually any C compiler.
To build with Make, run make assemblers in this directory. Alternatively,
the assembler can be built using CMake.
Two copies of the assembler will be produced: clownassembler and
clownassembler_asm68k. The latter provides the same command line interface as
SN 68k, while the former provides a custom, simpler, interface.
To regenerate the lexer and parser, install Flex and Bison and then run make.
This is Free Software, made available under the terms of the AGPLv3+. See the 'LICENCE.txt' file for more information.